Research On Nuclear Magnetic Permeability Evaluation Method Of Double Pore Medium Reservoir

As an important parameter of oil and gas exploration and development,permeability has guiding significance for evaluating reservoir production.Taking two different lithological reservoirs as the research object,this paper comprehensively analyzed the pore types of the reservoirs and the key parameters affecting the permeability by carrying out petrophysical experiments and combining the logging curve,and established a nuclear magnetic permeability model according to the functional relationship between each parameter and the permeability.In this paper,the combination of mercury pressure and NMR experiments was used to obtain data,and pore connectivity was characterized by drawing a superimposed diagram of mercury pressure curve and NMR T₂spectrum.The complex pore was studied by establishing the fractal dimension of NMR,and the heterogeneity of reservoir was quantitatively characterized,and the reliability of NMR fractal results were verified by combining mercury pressure and fractal dimension.The fractal dimension of capillary mean tortuosity is used to characterize the degree of fluid migration in pore.Finally,a new permeability model is established based on the NMR porosity,the correlation between the influencing factors and the pore throat structural parameters is analyzed and the conversion model between the two is established,and the pore throat structure parameters are obtained by using the NMR pseudo capillary pressure curve to realize the continuous measurement of downhole NMR permeability.By comparing with the Coates model,it is found that the calculation results of the new model are closer to the true permeability of the core.